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Collection, Preservation and Display of Old Lawn Mowers

back lapping technic

Hi !

I have just getting a Blade Sharpening Kit from oldlawnmowers company (thanks John !) but I wondering how to use it apply to my Atco Lightweight ?

The principle (as I understood) is to turn the cylinder in reverse with the grit lapping paste on each blade for rubbing on the fixed blade.

OK, fine !

Now, applied to my Atco, I don't know how to achieve it well :

  • Is there some unbolt something somewhere : I have noticed that the clutch is rubbing a little when I rotating back cylinder by hand ?
  • Do I have to turn the cylinder by hand or is it to slow and external mechanical is needed  to drive it quicker ?

I could ask directly John for sure but I think that this topic maybe helpful for other newbies like me !

Regards, Arnaud

 

 

Forums

hortimech Sun, 28/04/2013

yes, your understanding of the principle is correct, you just need to find a way to turn the cylinder in reverse. Set the cylinder to bottom blade, apply the water based grinding paste, note: never use oil based paste, now you have to spin the cylinder briskly in reverse. You may have to remove any drive chains etc to make this easier, you also may have to make an adapter of somesort if there isn't a bolt at the cylinder end. Rotate the cylinder for some time, checking the cylinder often, you are looking to get a dull grey line right across each cylinder blade, you may have to re-adjust the cylinder to bottom blade occasionally. Once completed, you will need to remove ALL the grinding paste before turning the cylinder forward, either with a pressure washer or hot soapy water.

There are machines available to turn the cylinder, these are just a small electric motor with a right angle gearbox fastened to to the motor to reduce the output speed to about 200rpm.

Having said all of the above, can I ask what you are trying to achieve, are you trying to keep a cylinder sharp, or are you going to try and sharpen a blunt cylinder & bottom blade? If the later, then I must point out that backlapping is a maintence method and will never sharpen a blunt cylinder.

 

arnob Sun, 28/04/2013

Hi hortimech,

Thanks a lot for the detailed answer.

The mower already cutting well, this is mainly to learn about how to maintain it in a good state and maybe increase the cut quality.

200 rpm means that I can't do it without external drive 

Disengage the chains is another point.

That was the information I needed !

Thanks a lot.

Maybe others Atco owners already have done this kind of operation and have to share detailled tips specially for the ligthweigh modfel ?.

Anyway, main data are aleady here : thanks once again.

Regards,

Arnaud

 

 

hortimech Sun, 28/04/2013

No, you can do it by hand, it just takes longer laugh

Toro GM3 triple mowers for golf greens used to come with a 3/8 drive brace to backlap the units by hand, the use of a backlap machine just makes it easier and quicker.

 

arnob Sun, 28/04/2013

OK, great !

I'll try by hand first and if it to boring, I'll seek a wireless drill system or something like that.

Regards,

Arnaud

wristpin Mon, 29/04/2013

Hand cranking may be boring but too much speed (power drill) will fling the grinding paste all over the place!

arnob Mon, 29/04/2013

Hi !

 

I have done a mount with a driller and to much speed is not a good idea indeed !
Despite that, I am very glad by the result now : very efficient operation.
The bad side is that due to the friction between blades, the mower is a little bit more noisier.
Regards,
 
Arnaud

Old Lawnmower … Wed, 08/05/2013

From The Old Lawnmower Company to Arnaud Boulay of Normandy.

Over a period of time, you have corresponded with us via email regarding the 1951 Light Atco that you purchased in France and this culminated in April this year with you buying a Grassbox and one of our Blade Sharpening Kits.  Since your first contact in October 2011, friendly communication and free advice have been forthcoming from my son John who you mention in your Forum post.

You now say, on a public forum… 'I could ask directly John for sure but I think that this topic maybe helpful for other newbies like me!'

The sensible, courteous thing to have done in the circumstances would have been to ‘ask directly John’ (sic) not just to have thrown it open to everyone in general on a public forum and by so doing cast doubt on the integrity of our product.  We have sold nearly 200 of these kits so far and you are, literally, the first person who has had an apparent problem with understanding the detailed instructions supplied with our Kit and that includes quite a few foreigners like yourself.

In future, if you have problems in understanding precise, comprehensive instructions, it might be better to come back first to the people who work every day on old (and new) lawnmowers and know what they are talking about rather than just invite comments from the legion of self-appointed experts who sit poised over their keyboards ready to air their ‘knowledge’ on Forums.

As regards your comment... 'The bad side is that due to the friction between blades, the mower is a little bit more noisier (sic).'  If you had read our instructions properly regarding the adjustment of the cylinder and bottom blade, you would have realised that any excessive noise is caused by the fact that you have not adjusted them properly – the components are too tight.

Just to get one thing straight, machine grinding of cylinders is only necessary when there has been serious damage to the assembly.  Using it in any other situation is unnecessary and, indeed, damaging, as it just takes years off the life of the cylinder, something that you certainly do not want to do with the often irreplaceable cylinders on old lawnmowers.

Setting aside for one moment our own experience of using backlapping to sharpen hundreds of cylinders (blunt or otherwise) for customers from mowers spanning a period of over a century, we would prefer to rest our case for this method on the advice from Ransomes, the world's first lawnmower manufacturers, who have been making them for 180 years.  They still recommend backlapping as the way to sharpen their top-flight greens and wicket mowers.  I think that they are likely to know a bit more about the subject than most other 'experts'.

Ivor Gregory, The Old Lawnmower Company.

www.oldlawnmowers.co.uk

hortimech Wed, 08/05/2013

[quote]

In future, if you have problems in understanding precise, comprehensive instructions, it might be better to come back first to the people who work every day on old (and new) lawnmowers and know what they are talking about rather than just invite comments from the legion of self-appointed experts who sit poised over their keyboards ready to air their ‘knowledge’ on Forums.

[quote]

Are you sugesting that I do not know what I am talking about? your very tone suggests that you and only you know about backlapping.

In my opinion, based on the fact that I server an apprenticeship as a lawnmower mechanic from 1973, gained my Parks & Grounds city and guilds and worked in the industry for nearly 40 years, you do not know what you are doing. You cannot sharpen blunt and rounded cylinder blades by backlapping, it is a maintenance procedure, you need (for want of a better term) square edges to the cylinder blades & the bottom blade for backlapping to work.

As for your referal to Ransomes, yes they made very good machinery until they got delusions of granduer and started buying up lawnmower companies, then the bean counters got hold of the company and ran it into the ground, at which point textron bought it and now most of the golf course machines that you see are actually re-badged Jacobsens

ajw2403 Fri, 31/05/2019

Hi hortimech,

Why should you never use oil based grinding paste for cylinder blade lapping?

Thanks

Best regards,

Anthony

wristpin Fri, 31/05/2019

Once a back lapping session is over, every trace of paste must be removed . Water based paste can be washed off, oil based cant. If paste remains on a cylinder that is then rotated in the working direction it will undo the the possible good done by back lapping.

Back lapping is only truly effective, and then only as a maintenance procedure, and then, only if the blades have previously been relief ground. It is the relief grinding that creates the small space on the back of each blade to trap the paste where it is needed to work effectively.

The so called sharpening kits will not recover a blunt cylinder and will be of limited use in putting an edge on a dull cylinder by back lapping unless there is relief to trap the paste. 

 

hortimech Fri, 31/05/2019

Cannot really add anything to what Wristpin said, except, isn't strange that Ivor Gregory never replied to my post, could it be that I am more qualified than he to be called an Expert ? ;-)

hortimech Tue, 04/06/2019

Please don't, they are basically a device that fastens to the bottom blade with a strip of abrasive that the cylinder runs against. There is no way to get the required angle on the cylinder blades and its use, usually leads to mis-shaped cylinders. There is also no way to reface the bottom blade, so using one is like sharpening one blade of a pair of scissors.

I have had to regrind cylinders that have supposedly been sharpened with these things and it always involved more time in the grinder than normal and removed more metal than normal. To put it bluntly, I would only buy one of these things if I wanted something to point to and say 'Do not buy one of these' ;-)

wristpin Tue, 04/06/2019

Not sure whether the one in question involves the clip on abrasive or is just a tin of grinding paste - either way, best avoided!

ajw2403 Tue, 04/06/2019

 

Thanks for the heads up guys - appreciate